Showcase how to integrate DB-specific functions (#201)

Augment `AdminService.Author` by 2 fields `age` and `lifetime` whose
values are computed by SQLite and HANA-specific functions.

Don't do this in bookshop directly, to keep it simple.  Instead, use
the fiori module, which also allows to integrate the fields in the UI.

Co-authored-by: Daniel <daniel.hutzel@sap.com>

fiori/test/requests.http

@@ -63,3 +63,15 @@ Content-Type: application/json
 
 ### Get active order
 GET {{bookshop}}/orders/Orders(ID={{newOrderID}},IsActiveEntity=true)
+
+### Create author
+POST {{bookshop}}/admin/Authors
+Content-Type: application/json
+Authorization: Basic alice:
+
+{
+  "ID": 200,
+  "name": "William Shakespeare",
+  "dateOfBirth": "1564-04-26",
+  "dateOfDeath": "1616-04-23"
+}